FDMF5821 datasheet(18/26 Pages) ONSEMI

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FDMF5821 • Rev. 1.0

Programmable Thermal Shutdown (P-THDN)

When the TMON pin voltage exceeds 1.5 V, the internal

comparator shuts down the driver (EN pin goes LOW).

The programmable thermal shutdown temperature

range can be adjusted by RTMON so that the shutdown

temperature can be customized. The equation below

shows the relationship between RTMON value in design

and desirable thermal shutdown temperature.

(2)

Figure 36 shows the relationship between RTMON and P-

THDN temperature. Increasing the RTMON value results

in a lower P-THDN temperature. The system designer

can define the shutdown temperature of FDMF5821

based on the system thermal design.

The P-THDN is a latch-off shutdown, so the (POR) on

VCC is needs to re-enable the gate driver. If not using

TMON / P-THDN features, tie the TMON pin to AGND.

100

200

P-THDN

Temp. [°C]

29.5 RTMON [kW]

* VTMON = 1.5 V, CTMON = 0.1 µF

25.9

150

Figure 36.

RTMON vs. P-THDN Temperature

Catastrophic Fault

SPS FDMF5821 includes a catastrophic fault feature. If

a HS MOSFET short is detected, the driver internally

pulls the EN / FAULT# pin LOW and shuts down the

SPS driver. The intention is to implement a basic circuit

to test the HS MOSFET short by monitoring LDRV and

the state of SW node.

If a HS short fault is detected, the SPS module clocks

the fault latch shutting down the module. The module

requires a VCC POR event to restart.

PWM

LDRV

(internal)

SW-Fault

(internal)

FAULT

(internal)

EN/FAULT#

Potential noise from

adjacent phases switching

HS FET short during

LS FET turning on

false trigger

Normal switching operation

EN/FAULT#

pulled LOW and

driver IC disabled

Figure 37.

Catastrophic Fault Waveform

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